[tracker-miners] Revert "extract: Remove DVI support"

[Sam Thursfield <sthursfield src gnome org>]

commit 11c1cb51737b3eef0de198b6cb79098f6b8fa48d
Author: Sam Thursfield <sam afuera me uk>
Date:   Mon Nov 2 17:35:34 2020 +0100

    Revert "extract: Remove DVI support"
    
    This reverts commit cf34b18dc18d048ec1e524469451a88f16134754.
    
    I accidentally pushed to master instead of opening an MR.

 meson_options.txt                         |   2 +
 src/tracker-extract/10-dvi.rule           |   6 +
 src/tracker-extract/tracker-extract-dvi.c | 249 ++++++++++++++++++++++++++++++
 3 files changed, 257 insertions(+)
---
diff --git a/meson_options.txt b/meson_options.txt
index 48c57aadb..3420973ab 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -30,6 +30,8 @@ option('network_manager', type: 'feature', value: 'auto',
        description: 'Connection detection through NetworkManager')
 option('abiword', type: 'boolean', value: 'true',
        description: 'Enable extractor for AbiWord files')
+option('dvi', type: 'boolean', value: 'true',
+       description: 'Enable extractor for DVI metadata')
 option('icon', type: 'boolean', value: 'true',
        description: 'Enable extractor for ICO metadata')
 option('mp3', type: 'boolean', value: 'true',
diff --git a/src/tracker-extract/10-dvi.rule b/src/tracker-extract/10-dvi.rule
new file mode 100644
index 000000000..5b6787182
--- /dev/null
+++ b/src/tracker-extract/10-dvi.rule
@@ -0,0 +1,6 @@
+[ExtractorRule]
+ModulePath=libextract-dvi.so
+MimeTypes=application/x-dvi
+FallbackRdfTypes=nfo:Document
+Graph=tracker:Documents
+Hash=@hash@
diff --git a/src/tracker-extract/tracker-extract-dvi.c b/src/tracker-extract/tracker-extract-dvi.c
new file mode 100644
index 000000000..8e32021ef
--- /dev/null
+++ b/src/tracker-extract/tracker-extract-dvi.c
@@ -0,0 +1,249 @@
+/*
+ * Copyright (C) 2012, Red Hat, Inc.
+ *
+ *   Code adapted from evince/backend/dvi/mdvi-lib/dviread.c
+ *   Copyright (C) 2000, Matias Atria
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ * Boston, MA  02110-1301, USA.
+ */
+
+#include <stdio.h>
+#include <fcntl.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <glib.h>
+#include <gmodule.h>
+
+#include <libtracker-extract/tracker-extract.h>
+
+#define __PROTO(x)     x
+extern gulong  fugetn __PROTO((FILE *, size_t));
+
+#define fgetbyte(p)    ((unsigned)getc(p))
+#define fuget4(p)      fugetn((p), 4)
+#define fuget3(p)      fugetn((p), 3)
+#define fuget2(p)      fugetn((p), 2)
+#define fuget1(p)      fgetbyte(p)
+
+
+#define DVI_ID         2
+#define DVI_TRAILER    223
+#define DVI_PRE                247
+#define DVI_POST       248
+
+typedef struct {
+       char *filename; /* name of the DVI file */
+       FILE *in;       /* from here we read */
+       char *fileid;   /* from preamble */
+       int npages;     /* number of pages */
+       int depth;      /* recursion depth */
+       gint32 num;     /* numerator */
+       gint32 den;     /* denominator */
+       gint32 dvimag;  /* original magnification */
+       int dvi_page_w; /* unscaled page width */
+       int dvi_page_h; /* unscaled page height */
+       int stacksize;  /* stack depth */
+} DviContext;
+
+gulong
+fugetn (FILE *p, size_t n)
+{
+       gulong v;
+
+       v = fgetbyte(p);
+       while (--n > 0) {
+               v = (v << 8) | fgetbyte(p);
+       }
+
+       return v;
+}
+
+static char *
+opendvi (const char *name)
+{
+       int len;
+
+       len = strlen (name);
+
+       /* if file ends with .dvi and it exists, that's it */
+       if (len >= 4 && g_strcmp0 (name + len - 4, ".dvi") == 0) {
+               g_debug ("Opening filename:'%s'", name);
+
+               if (access (name, R_OK) == 0) {
+                       return g_strdup (name);
+               }
+       }
+
+       return NULL;
+}
+
+static void
+mdvi_destroy_context (DviContext *dvi)
+{
+       g_free (dvi->filename);
+       g_free (dvi->fileid);
+
+       if (dvi->in) {
+               fclose (dvi->in);
+       }
+
+       g_free (dvi);
+}
+
+static DviContext *
+mdvi_init_context (const char *file)
+{
+       FILE *p;
+       gint32 arg;
+       int op;
+       int n;
+       DviContext *dvi;
+       char *filename;
+
+       /*
+        * 1. Open the file and initialize the DVI context
+        */
+       filename = opendvi (file);
+       if (filename == NULL) {
+               return NULL;
+       }
+
+       p = fopen (filename, "rb");
+       if (p == NULL) {
+               g_free (filename);
+               return NULL;
+       }
+
+       dvi = g_new0 (DviContext, 1);
+       dvi->filename = filename;
+       dvi->in = p;
+
+       /*
+        * 2. Read the preamble, extract scaling information
+        */
+       if (fuget1 (p) != DVI_PRE) {
+               goto error;
+       }
+
+       if ((arg = fuget1 (p)) != DVI_ID) {
+               g_debug ("Unsupported DVI format (version %u)", arg);
+               goto error;
+       }
+
+       /* get dimensions */
+       dvi->num = fuget4 (p);
+       dvi->den = fuget4 (p);
+       dvi->dvimag = fuget4 (p);
+
+       /* check that these numbers make sense */
+       if (!dvi->num || !dvi->den || !dvi->dvimag) {
+               goto error;
+       }
+
+       /* get the comment from the preamble */
+       n = fuget1 (p);
+       dvi->fileid = g_malloc (n + 1);
+       fread (dvi->fileid, 1, n, p);
+       dvi->fileid[n] = 0;
+       g_debug ("Preamble Comment: '%s'", dvi->fileid);
+
+       /*
+        * 3. Read postamble, extract page information (number of
+        *    pages, dimensions) and stack depth.
+        */
+
+       /* jump to the end of the file */
+       if (fseek (p, (long) - 1, SEEK_END) == -1) {
+               goto error;
+       }
+
+       for (n = 0; (op = fuget1 (p)) == DVI_TRAILER; n++) {
+               if (fseek (p, (long) - 2, SEEK_CUR) < 0) {
+                       break;
+               }
+       }
+
+       if (op != arg || n < 4) {
+               goto error;
+       }
+
+       /* get the pointer to postamble */
+       fseek (p, (long) - 5, SEEK_CUR);
+       arg = fuget4 (p);
+
+       /* jump to it */
+       fseek (p, (long) arg, SEEK_SET);
+       if (fuget1 (p) != DVI_POST) {
+               goto error;
+       }
+
+       fuget4 (p); /* offset */
+       if (dvi->num != fuget4 (p) ||
+           dvi->den != fuget4 (p) ||
+           dvi->dvimag != fuget4 (p)) {
+               goto error;
+       }
+       dvi->dvi_page_h = fuget4 (p);
+       dvi->dvi_page_w = fuget4 (p);
+       dvi->stacksize = fuget2 (p);
+       dvi->npages = fuget2 (p);
+
+       g_debug ("Postamble: %d pages", dvi->npages);
+
+       return dvi;
+
+error:
+       mdvi_destroy_context (dvi);
+       return NULL;
+}
+
+G_MODULE_EXPORT gboolean
+tracker_extract_get_metadata (TrackerExtractInfo *info)
+{
+       TrackerResource *resource;
+       GFile *file;
+       gchar *filename;
+       DviContext *context;
+
+       file = tracker_extract_info_get_file (info);
+       filename = g_file_get_path (file);
+
+       context = mdvi_init_context (filename);
+
+       if (context == NULL) {
+               g_warning ("Could not open dvi file '%s'\n", filename);
+               g_free (filename);
+               return FALSE;
+       }
+
+       resource = tracker_resource_new (NULL);
+
+       tracker_resource_add_uri (resource, "rdf:type", "nfo:PaginatedTextDocument");
+
+       tracker_resource_set_int64 (resource, "nfo:pageCount", context->npages);
+
+       if (context->fileid) {
+               tracker_resource_set_string (resource, "nie:comment", context->fileid);
+       }
+
+       mdvi_destroy_context (context);
+
+       tracker_extract_info_set_resource (info, resource);
+       g_object_unref (resource);
+
+       return TRUE;
+}